KITAKAMI, Japan – Engineers racing to cool a stricken nuclear plant in Japan partially restored power to a control room on Tuesday, as radioactivity in more foodstuffs fuelled anxiety over product safety.

An external electricity supply has now been linked up to all six reactors at the Fukushima No. 1 power station, more than a week after a 14-metre (46-foot) tsunami crippled the ageing facility.

In another small step towards regaining control of the plant, the lights came back on in the control centre of the number three reactor, making it easier for workers toiling to get the vital cooling systems working again.

"As of 10:43 pm (1343 GMT), the control centre for reactor number three had its lighting on," an official from plant operator Tokyo Electric Power Co. (TEPCO) told reporters late Tuesday.

The number three reactor is a particular concern because it contains a potentially volatile mixture of uranium and plutonium.

The twin quake and tsunami disaster, Japan's worst crisis since World War II, has left nearly 23,000 people dead or missing, with entire communities along the northeast coast swept away.

Now the shell-shocked nation faces an invisible threat from radiation seeping from the Fukushima plant, which lies just 250 kilometres (155 miles) from the greater Tokyo area and its 30 million inhabitants.

The health ministry advised residents in five towns or cities in Fukushima prefecture not to use tap water to make formula milk and other drinks for babies due to abnormally high radiation levels.

The government also ordered increased inspections of seafood after radioactive elements were detected in the Pacific Ocean near the Fukushima plant.

At one spot eight kilometres from the troubled plant, radioactive iodine 80 times the normal level was found.

The government has halted shipments of some foodstuffs in nearby prefectures after the discovery of higher-than-normal levels of radiation in milk and certain vegetables, but it insists there is no health hazard.

Raw milk in Ibaraki prefecture and broccoli in Fukushima were the latest products to show levels of radioactive materials beyond legal limits, Kyodo News said early Wednesday.

"Food products that present abnormal levels (of radiation) will not appear on the market, so please don't worry. And even if you put such foods in your mouth, they will not have an immediate health risk," said Consumer Affairs Minister Renho, who uses only one name.

Nevertheless, France has urged the European Commission to impose "systematic controls" on imports of fresh produce from Japan into the EU, amid fears of nuclear contamination.

Nuclear plant staff and technicians, firefighters and military personnel are struggling to regain control of the overheating facility but spikes in radiation levels have at times forced the crews to suspend work.

The UN's atomic watchdog confirmed Tuesday that the ageing Fukushima plant was still leaking radiation.

The government has declared an exclusion zone with a radius of 20 kilometres around the power station and evacuated tens of thousands of people, while telling those within 20 to 30 kilometres to stay indoors.

An executive of the under-fire plant operator bowed deeply and apologised at evacuee centres to people forced from their homes by the crisis.

"Since I have tried to manage this problem hand-in-hand with the government, my visit here to directly meet you was belated," said TEPCO vice president Norio Tsuzumi.

"For this I also apologise from the bottom of my heart."

The plant has been hit by a series of blasts since the March 11 tsunami, in the worst nuclear crisis since the Chernobyl disaster in the Soviet Union in 1986.

France's Nuclear Safety Authority warned that local contamination from the Japanese plant would last "for decades and decades".

Workers were forced to evacuate part of the facility on Monday when grey smoke rose from reactor number three, TEPCO said.

Smoke or steam was also seen rising from the number two and number three reactors Tuesday but work later resumed at the site.

Evacuees endured another night of freezing temperatures in overcrowded shelters, but aid was flowing into the affected areas in greater quantities, according to the UN Office for the Coordination of Humanitarian Affairs.

Some 533,000 people still had no household power and two million people were still without tap water, with 318,213 people huddled in evacuation centres across 16 prefectures, it reported.

But about 90 percent of the national highways damaged in the twin disaster are now open to the public and more than 90 percent of disrupted telecommunications have been restored, the UN agency said.

A series of strong quakes measuring above 6.0-magnitude rattled the northeast coast on Tuesday, keeping residents on edge, but there were no reports of damage or injuries.

Tokyo's stock market, which took a pummelling for most of last week, jumped 4.36 percent as the Bank of Japan pumped another two trillion yen ($24.67 billion) into the money market to calm jittery investors.